>>1820720Don't upload them to imgur, since they compress the images and make them blurry.
Most anime are produced at 720p, so most 1080p you get is upscaled. Take screenshots from 720p. Known exceptions are KyoAni (but they apply awful glows and filters), some JC Staff and some Xebec. And If the show is old, it was most likely made in 480p.
It also depends on the video encode. A shit encode will mess up everything in the video.
If you still want to improve them, try filters. Each screenshot is different, so you'll have to try different ones.